For bolt action rifles I put the rifle in a vise and bore sight it on a tennis ball at about 50 feet.Then I adjust the scope to the center of the tennis ball.It's amazing how close you can get.Obviously useless when you can't look down the bore.I have sighted in a couple of rifles this year for friends who had them bore sighted at the gun store with a laser or whatever.They were both within 6 inches at 100 yards.They work OK ,I'm just too cheap to buy one.